Why Does My Wood Stove Smoke

If your wood burning stove is spilling smoke back into your home as you light the fire, the first thing you should consider is the inside temperature of the stove. If the inside of the wood stove is cold, the cool air will funnel down the chimney and into the wood stove where it will remain trapped by the doors.
To prevent this from happening, open the doors on your wood stove and allow the wood stove interior to heat up for at least 30 minutes before you attempt to start a fire in it. Opening the doors will not only pre-heat the wood stove it will also jump start the draft and get it moving upwards.

At this point, you'll still want to check the draft. Light a match and see which way the flame moves. If it moves upward, the draft is good and moving as it should. If it moves downward you'll need to find a way to reverse the draft. You can use a starter block or a commercial wax log to redirect the draft upward. All you need to do is close the damper, start the starter block or wax log and place it near the flue opening. As the starter block or wax log burns, slowly open your damper so it can force air up the chimney and reverse the draft. You'll know when the draft is reversed because you'll hear the air sucking the fire and heat from the starter block at which time it will be safe to start your fire.

Wet or unseasoned firewood could also cause your wood stove to produce smoke when you light a fire. In order for firewood to burn safely and efficiently, you'll need to make sure that it is dried and properly seasoned. This means that it should be at a moisture content of 20% or less. You can measure the moisture content of your firewood with a moisture meter.

Why does my wood stove smoke when it's windy?

If smoke from your wood stove is spilling into your home on a windy day, your chimney may be too short. Taller chimneys work better since shorter chimneys will not pull the smoke out of the home very easily. They carry smoke farther away from the house than short chimneys and a longer chimney also reduces the risk of sparks landing on the surface of the roof. Building codes require chimneys to be at least 2 feet taller than any object within 10 feet, such as the roof surface or a dormer, or 3 feet taller than the peak of the roof. In some cases, these suggested heights may not be adequate to allow the chimney to draw air properly. For homes that are surrounded by trees or hills, or close to large bodies of water, you may need to extend the chimney height higher than the required 3 feet to improve wood stove efficiency.

If your chimney extends the required height above your roof and your wood stove is still back puffing into your home, you may need to put a chimney cap on the pipe. There are chimney caps that are specifically designed to stop wind from blowing into the chimney regardless of the wind direction. For example, VacuStack chimney caps deflect wind turning it into more of a venturi action causing the smoke to be sucked out of the chimney.

Just be sure you don't undersize your masonry flue by adding a VacuStack chimney cap. If this does not work or if you cannot find a VacuStack chimney cap that will not reduce your flue size, an Exhausto Fan will work.

Why does my wood stove smoke intermittently?

If your chimney lets out intermittent puffs of smoke into the room, this is known as downdraught. Downdraught is usually caused by a chimney that is either not high enough or where there are high buildings or trees nearby that affect the wind currents around the chimney. Often downdraught will only occur in certain conditions so you might find that it is only on days when the wind comes out of the North that the stove smokes in puffs due to downdraught.

Most of the time, raising the height of the chimney is the simplest solution to downdraught. If raising the height of the chimney doesn't work, fixing an anti-downdraught cowl will do the trick.

Why does my wood stove smoke all the time?

There are a number of things that could cause a wood burning stove to smoke continuously including an un-swept or blocked chimney, competition with another chimney or extractor, poor ventilation, excessive fireplace opening size in relation to the flue size, incorrect size of the chimney pot, an unlined or cold (un-insulated) chimney, pressure difference around building, or insufficient chimney height and therefore inadequate draw.

The easiest way to figure out which of the above causes is the reason for your wood stove smoking is to make a checklist and try to eliminate each cause. If your wood stove and chimney hasn't been cleaned recently, a good cleaning session may cure your smoking fireplace.

If you have another chimney in your house, this may have a stronger draw than the smoking chimney. It will be pulling air from any source and one of these sources may be the smoking chimney. Block off and cap any unused chimneys so that they cannot draw air from the house. If you have a stove on another chimney, close the air vents and door. If the smoking problem improves, the other chimneys are usually to blame as they are pulling smoke down the chimney.

Try opening a window or door in the room with the smoking wood stove. If that room does not have a window then open a window or external door in the room closest to the room with the smoking wood stove or stove and make sure that the doors between these two rooms are open.

If your wood stove is installed in an existing fireplace, try blocking off the top third of the fireplace with a non-combustible object. If the smoke improves, your fireplace opening may be too large. Try adding a smoke guard or recessed metal plate to the top of the fireplace opening to make it smaller.

Make sure that your chimney is high enough. Building codes require chimneys to be at least 2 feet taller than any object within 10 feet, such as the roof surface or a dormer, or 3 feet taller than the peak of the roof. If the chimney is too short, it will not pull the smoke out of the home.

If you have done any major renovations to your home especially those making it better insulated (which in turn means better sealed and less "breathing") this have caused pressure differential in your home. Consider checking into an outside air kit if you think your home is sealed better than before.